Pneumatic stapling device

ABSTRACT

A pneumatic stapler of the type having a working cylinder communicating with a surrounding air chamber by means of ports in the cylinder wall is provided with an annular valve means movable on the external surface of the cylinder wall. During the driving stroke of the piston said valve means closes the ports in the cylinder wall and opens an outlet passage for venting the air from the cylinder displaced by the piston and from the air chamber to the atmosphere. When the piston reaches the end of its driving stroke, said valve means opens the ports in the cylinder wall and connects the air chamber with a space beneath the piston and closes the outlet passage, whereby the piston is exposed to air pressure from the chamber for returning the piston to its initial position.

[4 1 Apr. 25, 1972 [54] PNEUMATIC STAPLING DEVICE Wilfried Lange, 1Brockhold, 3101, A1- tenhagen, Germany [22] Filed: Feb. 12,1970

[21] Appl.No.: 10,929

[72] Inventor:

[30] Foreign Application Priority Data Feb. 13, 1969 Germany ..P 19 07069.0

[52] US. Cl ..9l/398, 91/399, 91/404, 91/461 [51] Int. Cl ..F15b 15/22,F15b l3/042 [58] Field of Search ..91/399, 404, 461, 398; 92/85 [56]References Cited UNITED STATES PATENTS 3,396,636 8/1968 Bade ..9l/3993,479,926 11/1969 Hillier ..91/404 3,512,454 5/1970 Perkins ..92/85Primary Examiner-Paul E. Maslousky Attorney-Hibben, Noyes & BicknellABSTRACT A pneumatic stapler of the type having a working cylindercommunicating with a surrounding air chamber by means of ports in thecylinder wall is provided with an annular valve means movable on theexternal surface of the cylinder wall. During the driving stroke of thepiston said valve means closes the ports in the cylinder wall and opensan outlet passage for venting the air from the cylinder displaced by thepiston and from the air chamber to the atmosphere. When the pistonreaches the end of its driving stroke, said valve means opens the portsin the cylinder wall and connects the air chamber with a space beneaththe piston and closes the outlet passage, whereby the piston is exposedto air pressure from the chamber for returning the piston to its initialposition.

5 Claims, 2 Drawing Figures PATEHTEDAPR 25 m2 3, 557, 96a

SHEET 1 UF 2 ATTORNEYS PNEUMATIC STAPLING DEVICE DESCRIPTION The presentinvention relates to a pneumatic stapling device and especially to aportable device operable by compressed air and serving to drivefastening means such as staples and the like into a work piece by meansof a driver which is actuated by a piston operated by compressed air,which piston is returned to its initial position by pneumatic operation.

The prior art devices providing for a pneumatic return of the piston toits initial position have an additional storage chamber receiving theair which is necessary for moving the piston to its initial or retractedposition. Said storage chamber encloses the working cylinder andcommunicates with said cylinder by means of ports arranged in its sidewall. A first group of said ports is provided for admitting compressedair to the storage chamber from the interior of the working cylindertoward the end of the driving stroke of the piston. A second group ofports for admitting compressed air from the storage chamber to theinterior of the cylinder for effecting return of the piston from itsterminal position to its initial position provided adjacent the lowerend of the cylinder. Practical experience has shown that after eachworking stroke of the piston more compressed air is passed from theinterior of the cylinder into the storage chamber than is needed forreturning the piston. If the piston performs at very high speeds, theair displaced by the piston is pumped into the storage chamber whereby acounterpressure is produced which reduces the efficiency ofthe staplingdevice.

It is an important object of the present invention to provide acompressed air operated stapling device of the above type the piston ofwhich during its working stroke is not exposed to any counterpressureresulting from the air which is displaced by said piston.

Another object of the invention is the provision of a pneumatic staplerwith the interior of its working cylinder beneath the piston ventedduring the working stroke of said piston.

A further object of the invention is to provide a portable stapler witha piston pneumatically returned to its initial position, and the storagechamber of which receives no increase of air pressure during a rapidsequence of working strokes.

These and other objects and features of the present invention willbecome apparent from the following description taken in conjunction withthe accompanying drawings in which an embodiment of the invention isillustrated by way of an example. In the drawings FIG. 1 is afragmentary sectional view of a pneumatic stapler embodying thisinvention with the piston in its initial position, and

FIG. 2 is a similar view with the piston in its terminal position aftercompletion of its working stroke.

The invention comprises a pneumatic valve means for directly exhaustingthe storage chamber and the interior of the working cylinder beneath thepiston to the atmosphere during its working stroke. Preferably anannular slide valve is provided with pressure faces which are ofdifferent size and are directed opposite one another. Said slide valvecomprises a check valve for the admission of compressed air. Saidannular slide valve encloses the lower end of the working cylinder andhas transverse ports for venting the air contained in the storagechamber. These transverse ports together with venting openings of theworking cylinder open in an annular passage formed between said annularslide valve and the working cylinder. Said cylinder communicates withventing openings leading to the atmosphere. The pressure face of theannular slide valve effecting its descending motion is greater than thepressure face which effects its upward motion. The face effecting theupward motion is always acted on by compressed air.

The provision of the pneumatic valve means according to the inventionprovides during each working stroke of the piston an intense venting ofthe storage chamber and of the interior of the working stroke beneaththe piston. Thus when the working strokes are repeated very rapidly, airfrom the interior of the cylinder cannot be pumped into the storagechamber. Therefore, the staplers embodying the invention are especiallyadapted for a rapid sequence of working strokes as is the case withautomatic devices.

Referring now to the drawings, a body casing l of a portable pneumaticstapler encloses a working cylinder 2 with a side wall and a bottom endwall having a. storage chamber 3 surrounding the cylinder. In thecylinder 2 a piston 4 is reciprocable and is secured to a driver 5. Inthe lower portion of the working cylinder 2 transverse ports 14 and 18are arranged, which connect the cylinder with the atmosphere and thestorage chamber 3, respectively. A step shaped annular slide valvemember 6 surrounds the lower portion of the working cylinder which isprovided with said transverse ports 14 adjacent the end of the cylinderand ports 18 intermediate the ends of the cylinder. The slide valvemember 6 has two opposed pressure faces 7 and8. Pressure face 8 isgreater than the other pressure face 7. First passage means includingtrans verse bores 10 in the slide valve member 6 communicate theinterior of the cylinder with the storage chamber 3 by means of theintermediate ports 18 in the side wall of the cylinder 2. The slidevalve member 6 is provided with a second passage means includingtransverse ports 11 which open into an annular chamber 12 whichcommunicates with ports 14 on the lower end of the cylinder side wall.The annular chamber 12 communicates with outletpassages 13 adjacent thebottom wall of the body casing and connects said annular chamber 12directly with the atmosphere when the slide valve 6 is in the positionshown in FIG. 1.

In the upper terminal position of the annular slide valve member 6 as isshown in FIG. 1 of the drawings the upper pressure face 8 is adjacent ashoulder 15 of the side wall of the working cylinder, the shoulder 15limiting the travel of the valve 6. The lower face 7 of the slide valvemember 6 is permanently exposed to the pressure of the compressed aircontained in an air reservoir :19 which communicates by means of apassage 16 with the space7 beneath the pressure face 7. The annularslide valve member 6 by sealing rings 20 is closed off against theexternal surface of the working cylinder 2. An elastic ring 9 insertedin an annular recess 17 encircling the bores 10 serves as a check valvefor the slide valve member 6 to permit air to pass only into the chamber3.

The air reservoir 19 communicates by means of a control valve 21manually actuated by a trigger level 22 with a firing valve 23, which inits initial position as shown in FIG. 1 is exposed to the pressure ofthe air contained in the air reservoir 19 via control valve 21. Whencontrol valve 21 is lifted to its upper terminal position by means oftrigger level 22, the air acting on the firing valve 23 can escape tothe atmosphere via the venting openings 24 and 25, as is illustrated inFIG. 2. The air under pressure contained in reservoir 19 moves thefiring valve 23 upward, enters the working space 2' of the cylinder andacts upon the upper face of the piston 4 and moves it in its workingdirection. Beneath piston 4 the interior of the working cylinder via theports 14, the annular chamber 12 and the openings 13 is completelyvented. Also the storage chamber 3 at this moment is also connected tothe chamber 12 by the ports 11 and contains no air under pressure, sothat the annular slide valve member 6 by means of the lower pressureface 7 is held in its upper position.

When the piston 4 has proceeded the largest part of its working strokeand has passed the ports 18, it opens the ports 18 in the cylinder sidewall for admission of air under pressure from the interior of theworking cylinder into the storage chamber 3. First the annular slidevalve member 6 is moved downward to its lower terminal position. by theair acting on its upper face 8, whereby the openings 113 are closed. Theair under pressure has free access to the storage chamber 3 and inaddition flows beneath the piston 4 via the ports 11 of the slide valvemember 6 and the transverse ports 14 of the cylinder side wall.

When the control valve 21 returns to its lower terminal position uponrelease of the trigger 22, air under pressure acts again on the uppersurface of the upper end of the firing valve 23 and moves it downward,whereby the connection of the working cylinder 2 with the air reservoir19 is blocked. Simultaneously a connection to the venting openings 25 isproduced and the air contained in the working cylinder 2 above thepiston 4 escapes to the atmosphere. The air from the storage chamber 3enters the return space 2" of the working cylinder beneath the piston 4and moves it in a return stroke to its initial or retracted position asis illustrated in FIG. 1.

The upper frontal face 26 of the annular slide valve member 6 (see FIG.2) is so dimensioned that the air contained in the storage chamber 3 canhold the valve member 6 in its lower terminal position till the pistonhas reached its upper terminal position.

The present invention is of considerable advantage for pneumaticequipment of all kinds, and in particular for portable pneumaticpercussion devices having a rapid series of working strokes. This is ofparticular importance where the percussion device is concerned fordriving in staples, nails and other fasteners, so widely used in massproduction. The invention is also of importance for pliers and packingdevices for stapling the lids of cardboard boxes.

What i claim is:

1. In a pneumatic stapling device including a body portion containing anair reservoir, a cylinder having a side wall and a wall at one endthereof, an air storage chamber surrounding said cylinder, a pistonreciprocable in a working stroke and a return stroke in said cylinderand separating said cylinder into a working space on one side of saidpiston and a return space on the other side of said piston, and outletpassage means for venting said return space and said air storage chamberduring said working stroke, said cylinder having valve means at theother end thereof for admitting compressed air from said air reservoirinto said working space of said cylinder for moving said piston in saidworking stroke, said cylinder having first port means in said side wallof said cylinder to connect said working space to said air storagechamber to fill said air storage chamber and second port means in saidcylinder to connect said air storage chamber to said return space formoving said piston in said return stroke and for venting said returnspace; the improvement comprising a pneumatic valve for exhausting saidreturn space of said cylinder and said air storage chamber through saidoutlet passage means, said pneumatic valve having first passage meanscommunicating said air storage chamber with said first port means andsecond passage means communicating said air storage chamber with saidsecond port means, said first passage means including a check valvepermitting air to flow only from said working space into said airstorage chamber, said pneumatic valve having two opposed faces, one ofsaid faces being in communication with said cylinder and the other ofsaid faces being in permanent communication with said air reservoir,said one face being larger than said other face, said pneumatic valvebeing slidable on said cylinder to an open position by compressed airfrom said air reservoir acting on said other face and to a closedposition by compressed air from said working space of said cylinderacting on said one face, in said open position said pneumatic valveconnecting said return space of said cylinder and said air storagechamber to said outlet passage means during the working stroke, and insaid closed position said pneumatic valve closing ofi said return spaceand said air storage chamber from said outlet passage means during thereturn stroke.

2. The device of claim 1, wherein said cylinder has a shoulderengageable by said one face to limit the movement of said pneumaticvalve to its open position.

3. The device of claim 1, wherein said body portion includes a passagepermanently communicating said other face of said pneumatic valve withsaid air reservoir.

4. The device of claim 1, wherein said check valve comprises an elasticring and said first passage means includes at east one transverse borein said pneumatic valve, said elastic ring covering said bore.

5. The device of claim 4, wherein said first passage means furtherincludes an annular recess on said pneumatic valve, said elastic ringbeing located in said recess.

1. In a pneumatic stapling device including a body portion containing anair reservoir, a cylinder having a side wall and a wall at one endthereof, an air storage chamber surrounding said cylinder, a pistonreciprocable in a working stroke and a return stroke in said cylinderand separating said cylinder into a working space on one side of saidpiston and a return space on the other side of said piston, and outletpassage means for venting said return space and said air storage chamberduring said working stroke, said cylinder having valve means at theother end thereof for admitting compressed air from said air reservoirinto said working space of said cylinder for moving said piston in saidworking stroke, said cylinder having first port means in said side wallof said cylinder to connect said working space to said air storagechamber to fill said air storage chamber and second port means in saidcylinder to connect said air storage chamber to said return space formoving said piston in said return stroke and for venting said returnspace; the improvement comprising a pneumatic valve for exhausting saidreturn space of said cylinder and said air storage chamber through saidoutlet passage means, said pneumatic valve having first passage meanscommunicating said air storage chamber with said first port means andsecond passage means communicating said air storage chamber with saidsecond port means, said first passage means including a check valvepermitting air to flow only from said working space into said airstorage chamber, said pneumatic valve having two opposed faces, one ofsaid faces being in communication with said cylinder and the other ofsaid faces being in permanent communication with said air reservoir,said one face being larger than said other face, said pneumatic valvebeing slidable on said cylinder to an open position by compressed airfrom said air reservoir acting on said other face and to a closedposition by compressed air from said working space of said cylinderacting on said one face, in said open position said pneumatic valveconnecting said return space of said cylinder and said air storagechamber to said outlet passage means during the working stroke, and insaid closed position said pneumatic valve closing off said return spaceand said air storage chamber from said outlet passage means during thereturn stroke.
 2. The device of claim 1, wherein said cylinder has ashoulder engageable by said one face to limit the movement of saidpneumatic valve to its open position.
 3. The device of claim 1, whereinsaid body portion includes a passage permanently communicating saidother face of said pneumatic valve with said air reservoir.
 4. Thedevice of claim 1, wherein said check valve comprises an elastic ringand said first passage means includes at least one transverse bore insaid pneumatic valve, said elastic ring covering said bore.
 5. Thedevice of claim 4, wherein said first passage means further includes anannular recess on said pneumatic valve, said elastic ring being locatedin said recess.